We are investigating the interaction of plasma low density lipoproteins and high density lipoproteins with the liver cell membrane using a homologous system of porcine lipoproteins, isolated liver cell membranes and intact liver cells in primary culture. We are examining lipoprotein specificity of the membrane and are exploring the lipoprotein structural features responsible for specific binding using a combination of inhibitors and the selective modification of lipoproteins and cell membranes. The lipoprotein binding reaction in liver will be compared with that in fibroblast membranes. We will attempt to isolate a liver cell membrane protein or glycoprotein that interacts specifically with the lipoproteins, and to seek evidence for its surface location and involvement in binding in intact hepatocytes, by using antibodies to the binding component(s) as inhibitors of binding by intact cells. The studies should provide insight into the mechanism of specific lipoprotein binding in normal tissues and has relevance to the pathogenesis of atherosclerosis in humans.